JPS63149334A - Production of burnt agglomerated ore - Google Patents

Abstract

PURPOSE:To produce burnt agglomerated ore having excellent dropping strength under high product yield and productivity by pelletizing into green pellet having the specific grain size distribution while adding flux to the powdery iron ore and burning as coating powdery coke on the surface. CONSTITUTION:At the time of producing the burnt agglomerated ore as the raw material for blast furnace or the raw material for directly reducing iron- making by an endlessly moving grate type burning furnace, at least one kind of material or more among lime, slaked lime, limestone, bentonite, dolomite, water granulated blast furnace slag are added as flux to the iron ore and kneaded together with water to pelletize, and the green pellet having 3-13mm grain size and 8-9% moisture content is produced. This is sieved into fine grain having <5mm grain size and coarse grain >=5mm grain size, and it is blended, so that fine grain is contained at 15-40wt% and coarse grain as the remaining part. The surface of this green pellet is coated, with powdery coke at 2.5-4.0% ratio, and the burnt agglomerated ore having large dropping strength after burning is produced under high product yield and productivity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for producing calcined agglomerates suitable as raw materials for blast furnaces or directly reduced iron.

[Prior art and its problems]

Calcined agglomerate, which is made by pelletizing powdered iron ore and calcining it, is known as a raw material for blast furnaces or direct reduction iron manufacturing.
Its use is expanding.

This calcined agglomerate ore is usually produced as follows.

That is, a solvent consisting of at least one of quicklime, slaked limestone, bentonite, granulated blast furnace slag, dolomite, etc. is added to powdered iron ore having a particle size of about 8I or less to reduce the amount of CaO/5i02 in the calcined agglomerated ore. Value is 1.0-2.5
Add to the desired amount and mix with a mixer. Then, the obtained mixture is supplied to a disk-shaped first granulator, water is added thereto, and the mixture is granulated by the first granulator to produce raw pellets with a particle size of, for example, about 3 to 13+*. Form into. Next, the obtained raw pellets were fed to an e-disk type second granulator, and were subjected to 2.5-4. Approximately Owt% of coke powder is added and the green pellets are further granulated by a second granulator, thereby preparing green pellets whose surfaces are coated with coke powder.

The green pellets thus obtained are charged into an endless moving grate type kiln, and the layer of the charged green pellets is placed on the grate of the kiln, and then placed in the drying zone of the kiln.
Pass through the ignition zone and firing zone in sequence. In the dry zone, the raw pellet layer is heated from above at a temperature of 150 to 350°C.
Blow in drying gas to dry the raw pellets. In the ignition zone, high-temperature combustion gas is blown into the layer of dried green pellets from above to ignite the coke powder on the surface of the green pellets. In the combustion zone, the hot combustion gas produced by the combustion of coke breeze is sucked downward through the green pellet bed to heat the green pellets to the calcination temperature. The green pellets consist of fired pellets bonded by at least one of calcium ferrite and slag formed on their surfaces by heating in the firing zone. It is fired into large block-shaped lumps of calcined agglomerate.

The calcined agglomerate in the form of large blocks thus obtained is discharged from the downstream end of the calcining furnace, crushed by a crusher, and then sieved by a screen to obtain particles with a particle size of 3III less than 1 m. The sifted calcined agglomerate pieces are removed, and thus the calcined agglomerate ore has a maximum particle size of about 50 m + W in the form of a lump formed by combining a plurality of calcined pellets, and the particle size 3 to 13 in the form of a single calcined pellet. Calcined agglomerate of the size of a throat is produced.

The calcined agglomerate ore produced as described above has excellent reducibility, since it mainly contains a large amount of fine calcium ferrite and fine hematite, which have excellent reducibility. In addition, not only in the case of a lump-like shape in which multiple fired pellets are combined, but also in the case of a single fired pellet, it has an irregular shape, so when charged into a blast furnace, Since the reducing gas does not flow biasedly toward the center of the blast furnace, and gaps are formed between the fired agglomerated ores, smooth passage of the reducing gas is not obstructed. Furthermore, even if it collapses due to impact or the like during transportation, the calcined agglomerate, which is a lump of a plurality of calcined pellets combined, will simply separate into a single calcined pellet, so it can be used without any problem.

However, in the past, raw pellets with a particle size of about 3 to 13 mm obtained by the first granulator were used as they were, so the blending ratio of raw pellets with a large particle size was relatively high. When pellets are coated with coke powder and fired in a firing furnace, the product yield, production rate, and falling strength of the resulting fired agglomerates are not necessarily high.

[Purpose of the invention]

In view of the above-mentioned current situation, this invention consists of raw pellets made by adding 7 Jl of a solvent to powdered iron ore, coating them with coke powder, and charging the raw pellets into an endless moving grate type kiln. When continuously producing calcined agglomerate ore, by selecting the particle size of the green pellets used and their blending ratio, calcined agglomerate ore with high falling strength can be easily produced with a high product yield and production rate. The purpose is to

[Summary of the invention]

In this invention, raw pellets made by adding a solvent to powdered iron ore and granulating them are coated with coke powder, and the raw pellets are charged into an endless moving grate type kiln and fired continuously. , in a method for producing calcined agglomerate ore, in which the calcined agglomerate ore is continuously produced, the raw pellets have a particle size of 5fi;
The method is characterized in that raw pellets with a composition of 15 to 40 vrt% of the following and the remainder of the particle size of more than 5 fi are used, coated with the coke powder and charged into the kiln.

[Structure of the invention]

Hereinafter, the method for producing calcined agglomerate ore of the present invention will be described in detail.

The inventors of the present invention have developed coke powder into raw pellets granulated by adding a solvent to powdered iron ore. When the raw pellets are coated and charged into an endless moving grate kiln to continuously produce fired agglomerates, the product yield and production rate of the fired agglomerates are improved, and the falling strength is reduced. In order to improve this, we have repeatedly considered the raw pellets we use.

If the blending ratio of small-diameter green pellets increases and the particle size of the green pellets used becomes relatively small, the sinterability of the green pellets will be good, and the product yield of fired agglomerate ore can be improved. It is expected that. However, if the blending ratio of small-diameter green pellets is too large, the air permeability between the green pellets will deteriorate, requiring a long time for calcination and reducing the production rate of calcined agglomerate ore. In addition, when raw pellets are heated excessively, they easily melt, producing glassy slag, which reduces the falling strength of fired agglomerates and increases the molten structure, resulting in reduced reduction rate and reduction powdering rate. is also expected to worsen.

Therefore, an experiment was conducted in which raw pellets were used with various particle sizes and their blending ratios, and were coated with coke powder to produce fired agglomerate ore.

Then, the product yield, production rate, and falling strength of the calcined agglomerate ore were investigated.

As a result, if we use raw pellets with a composition consisting of 15-cowt% of particles with a particle size of 5M or less and the remainder of particles with a particle size of more than 5M, it is possible to achieve a higher product yield and productivity than when coated with coke powder and fired. It has been found that it is possible to produce calcined agglomerate at a high rate, and its drop strength can be significantly improved.

Figure 1 is a graph showing the relationship between the blending ratio of raw pellets with a particle size of 5 square meters or less in the raw pellets used and the product yield of the obtained calcined agglomerate, and Figure 2 is a graph showing the relationship between Particle size 5
Figure 3 is a graph showing the relationship between the blending ratio of raw pellets with a grain size of 5 mm or less and the production rate of the obtained calcined agglomerates, and the graph shows the relationship between the blending ratio of raw pellets with a grain size of 5 mm or less and the resulting calcined agglomerate. It is a graph showing the relationship with the falling strength of agglomerate ore. The particle size of powdered iron ore is approximately 8m or less, and the amount of coke powder added is 3.5m.
The test was carried out under the condition of wt%.

As shown in Figure 1, as the blending ratio of green pellets with a grain size of 5fi or less increases, the sinterability of the green pellets improves, so the product yield of calcined agglomerates increases, and the blending ratio increases. When the ratio is 1 5 wt% or more, the product yield is approximately 78% or more.

On the other hand, the production rate of calcined agglomerates is as shown in Figure 2, when the blending ratio of raw pellets with a grain size of 5 or less is 4 o vt.
% is approximately constant and is more than 1.5 tons/go・h, but if the blending ratio exceeds 40 vt%, the air permeability deteriorates and the firing time increases, so the production rate is approximately 1.5 tons/h. /-・
It tends to fall below h. As shown in Figure 3, the fall strength of calcined agglomerates decreases as the blending ratio of green pellets with a grain size of 54 or less increases, as the amount of glassy slag increases. If it exceeds 40 wt.%, the drop strength tends to fall below approximately 90 inches.

Therefore, in order to achieve a product yield of 78 inches or more after firing and agglomeration, a production rate of 1.5 tons/-h or more, and a drop strength of 90% or more, it is necessary to ~40
Raw pellets with a formulation consisting of % vrt and the remainder having a particle size greater than 5 m should be used.

In this invention, as described above, the particle size of 5 or less is 1
Using raw pellets with a composition of 5 to 4 wt% and the remainder having a particle size of more than 5+*, this is coated with coke powder and fired to improve the product yield, production rate, and falling strength of fired agglomerate ore. It is something that improves.

In this invention, the particle size of the powdered iron ore used is preferably about am or less, as in the prior art. This is 1 grain size 8m
This is because fine iron ore with a grain size of 8 days or less can be used as is even if it is not converted into a fired agglomerate mineral.

In this invention, the amount of coke powder coated on the green pellets is 2.5 to 4. It is preferable to set it as owt, %. This means that the amount of coated coke powder is 2.5wt.
If the amount is less than 4, the firing efficiency of the green pellets in the kiln cannot be increased, and the green pellets cannot be fired into high-strength calcined agglomerates in a short time. This is because if it exceeds 0 wt, the temperature of the raw pellet during firing becomes too high, and the structure of the fired agglomerate becomes too dense.

〔Example〕

Fine iron ore having the particle size composition shown in Table 1 and the chemical composition shown in Table 2, and coarse iron ore having the particle size structure shown in Table 3 and the chemical composition shown in Table 14. stone 40vr
t%, coarse grained iron ore at a ratio of 60 vrt%, and 2.7 wt% of quicklime having the particle size composition shown in Table 5 as a solvent and binder was added and mixed, and the resulting mixture was granulated. By doing so, green pellets with a particle size of about 3 to 13 tons and a moisture content of 8 to 100 kg were formed.

Next, the obtained raw pellets are sieved into particles with a particle size of 5 or less and particles with a particle size of more than 5, and raw pellets with a particle size of 51 or less and particles with a particle size of 5 or less are separated.
and raw pellets were blended in proportions within the scope of this invention, as shown in Table 6.

For comparison, raw pellets with a particle size of 5 m or less, raw pellets with a particle size of more than 5 m, and gold were mixed in proportions outside the range of the present invention, as shown in Table 6.

Table 6 (wt, chi) Next, powdered coke having the particle size distribution shown in Table 7 was added to the raw pellets of these formulations for 3. swt% added and granulated,
The surface of the raw pellets was coated with coke powder.

Next, the green pellets are charged to a thickness of 400 Ill+ on the grate of an endless moving grate kiln, and the green pellets are sequentially moved through the drying zone, ignition zone, and firing zone of the kiln, and are turned into fired agglomerates. Fired. The large block-shaped calcined agglomerate thus obtained is discharged from the downstream end of the kiln, and after being crushed by a crusher, the unsifted calcined agglomerate pieces having a particle size of less than 3ffI11 are removed by a screen. In this way, fired agglomerate in the form of a lump with a maximum grain size of approximately 50 grains, in which a plurality of fired pellets were combined, and a fired agglomerate in the form of a single fired pellet, with a grain size of approximately 3 to 13 grains, were produced. .

The product yield, production rate, and falling strength of the calcined agglomerates produced as described above were as shown in Table 8.

Table 8 As shown in Table 8 (=, in non-inventive parts 1 to 4 in which green pellets with a composition within the scope of the present invention were used, coated with coke powder and fired, Agglomerate ore yield is over 70%, production rate is 1.5 tons/rr
? - Over h, the drop strength was high at over 90%. In contrast, using raw pellets with a composition within the scope of this invention,
In Comparative Examples Ugly 5 and 6, which were coated with coke powder and fired, the yield or production rate of the calcined agglomerates was lower than Ugly 1 to 4 of the present invention.

〔Effect of the invention〕

According to this invention, by selecting the particle size of the green pellets used and their blending ratio, it is possible to easily produce calcined agglomerate with a high product yield and production rate, as well as high falling strength. .

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between the blending ratio of raw pellets with a grain size of 5 mm or less in the raw pellets used and the product yield of the obtained calcined agglomerates, and Figure 2 is a graph showing the relationship between the raw pellets with a grain size of Figure 3 is a graph showing the relationship between the blending ratio of raw pellets with a grain size of 51 mm or less and the production rate of the obtained calcined agglomerates.
It is a graph showing the relationship between the blending ratio of raw pellets and the falling strength of the obtained calcined agglomerates.

Claims (1)

[Claims] Raw pellets made by adding a solvent to powdered iron ore and granulating them are coated with coke powder, and the raw pellets are charged into an endless moving grate kiln and fired continuously, Thus, in the method for producing calcined agglomerate ore in which calcined agglomerate ore is continuously produced, the raw pellets are 15 to 40w with a particle size of 5 mm or less.
A method for producing calcined agglomerate ore, characterized in that raw pellets having a composition of t% and the remainder having a particle size of more than 5 mm are used, and the raw pellets are coated with the coke powder and charged into the calcining furnace.